Internal fluid shut off for hydraulic motor



June 1957 H. J. SHAFER 2,795,212

INTERNAL FLUID SHUT OFF FOR HYDRAULIC MOTOR Filed May 28, 1956 4 Sheets-Sneet 1 FIG. 2

JNVENTOR.

HOMER a. SHAFER ATTORPEYS June 11, 1957 H. J- SHAFER 2,795,212

INTERNAL FLUID SHUT OFF FOR HYDRAULIC MOTOR Filed May 28, 1956 4 Shee'ts-Sneet 2 Y I .0 5 lo f 7643A 4 51 '3 (F 40 5 35 36 M 67 FIG. 6 VENTOR- Y HOMER J. I SHAFE'R B 11 WWW ATTORNEYS H. J. SHAFER June 11, I957 INTERNAL FLUID SHUT OFF FOR HYDRAULIC MOTOR.

Filed May 28, 1956 4 Sheets-Sheet 3 FIG. 4

IN VENTOR. HOMER J. SHAFER By 8Z3 ATTORNEYS June 11, 1957 x H. J. SHAFER 2,795,212

INTERNAL FLUID SHUT OFF FOR HYDRAULIC MOTOR FiledMay 28, 1956 4 Sheets-Sheet 4 FIG. ,9-

, mmvrok HOMER J. HAFER 40 41' 2 38 ATTORNEYS United States PatentO INTERNAL FLUID SHUT OFF FOR HYDRAULIC MOTOR Homer J. Shafer, Mansfield, Ohio, assignor to Shafer Valve Company, Mansfield, Ohio, a corporation of Ohio Application May 28, 1956, Serial No. 587,757

10 Claims. (Cl. 12197) The invention relates generally to hydraulic motors having a rotary impeller vane, and more particularly to novel means for preventing leakage of pressure fluid from the motor during operation. This application is a continuation in part of my copending application Serial No. 333,496, filed January 27, 1953, which has matured in Patent No. 2,778,338, dated January 22, 1957.

Hydraulic motors of the character referred to have many applications. By way of example, such a motor is shown and described as adapted for operating valves in high pressure pipe lines transporting oil, gas, gasoline, or other fluids. Such motors may operate rotary plug valves in the pipe line and the motor may be actuated automatically by a change in line pressure caused, for example, by a break in the line, or may be actuated by remote control manually or automatically. In either case the power for actuating the motor may be applied for a substantial period of time after the valve is operated.

A substantially fluidtight seal is provided between the impeller vane and cylinder wall of the motor to separate the pressure chamber from the exhaust chamber, but when power is applied to the pressure chamber to rotate the vane, the pressure fluid tends gradually to flow or seep past the seal and leak out through the exhaust chamber port, particularly when high pressure continues to be applied after the vane has been rotated to its limit in one direction, as in the case of the motor closing a pipe line valve. The pressure fluid in the motor may be oil, gas, air, or other suitable fluid, and cumulative leakage resulting from continued operation may be expensive and may interfere with the balance of fluid in the pressure and exhaust chambers of the motor where the fluid operates in a. closed system.

Such a closed system may include oil pressure tanks connected with and maintaining the pressure and exhaust chambers of the motor filled with oil, the fluid pressure source for operating the motor being connected to the tanks for forcing the oil from one tank into the pressure side of the motor and exhausting oil from the exhaust side of the motor into the other tank. The balance of oil in the tanks must be maintained so as to insure that motor chambers are always filled with oil in all positions of the motor.

It' is an object of the present invention to provide a novel shut-off device for preventing leakage of pressure fluid in a rotary oscillatory hydraulic motor after the motor is operated in one direction or the other.

Another object is to provide an improved hydraulic motor having a rotary impeller vane with novel internal shut-off means closing off the pressure fluid n the exhaust side of the vane when the vane reaches its limit in either direction.

A further object is to provide novel shut-ohmeans mounted on the impeller vane of a rotary hydraulic motor for closing the pressure fluid exhaust port at the limit ice A still further object is to provide novel shut-off means which will prevent leakage of pressure fluid from the exhaust side of the motor after the pressure has been shut off and has equalized on both sides of the vane.

These and other objects are accomplished by the improvements comprising the present invention, a preferred embodiment of which is shown and described herein by way of example. It is to be understood that Various changes and modifications in details may be made without departing from the scope of the invention as defined in the appended claims.

Referring to the drawings:

Fig. 1 is a side elevational view of the hydraulicmotor of the present invention line valve;

Fig. 2 is an enlarged top view of the motor with the top plate removed and showing the vane at the limit of its movement in one direction;

Fig. 3 is a similar view showing the vane at the limit of its movement in the opposite direction;

Fig. 4 is a vertical sectional view through the motor removed from the valve, taken on line 4-4 of Fig. 3;

Fig. 5 is a reduced plan sectional view on line 5-5, Fig. 4; r

Fig. 6 is a similar view on line 66, Fig. 4;

Fig. 7 is a fragmentary perspective view of one of the specially designed rings for fitting in the shoes orabutments in the pressure chamber;

Fig. 8 is a fragmentary view similar to Fig. 2, showing a modified form of shut-off with the vane in a position just prior to closing the shut-off; and

Fig. 9 is a similar view showing the position of the vane after the shut-off has closed and the pressure has equalized on opposite sides of the vane.

The hydraulic motor of the present invention, indicated generally at 10, is shown in Fig. I mounted on the valve stem of a high pressure valve 11 of the rotary plug type mounted in a pipe line of which 12 and 13 are sections. Referring to Fig. 4, the rotor 14 of the motor is provided with an axial socket 15 at its lower end into which the valve stem is keyed in a usual manner, and the motor operates the valve. This application of the motor is shown by way of example, and it is to be understood that the invention embraces all other uses of the motor which are within the scope of the appended claims.

, As shown in Figs. 1 and 4, the rotor 14 is provided with an axial shaft 16 at its upper end, on which is mounted a worm sector 17 and a worm 18 is operable by'a hand wheel 19 for manually operating the valve. A key/"'20 is provided for connecting the worm sector to the motor when manual operation is desired, in which case the key is inverted from the position shown and inserted in the keyway 21. In the position shown a cross pin 22 holds the key disengaged from the sector to allow operation of the valve by the motor, but connects the motor shaft to an indicator ring 23 rotatable on top of the gear case 24 for indicating the position of the valve. A lubricating device 25 is mounted ontop of the motor for forcing lubricant through the bore of the rotor to the plug in valve 11. This device may be similar in construction to that shown in my copending application Serial No. 189,810, filed October 12, 1950,'now Patent No. 2,780,432, dated February 5, 1957. The bearing construction of the rotor shaft in the plates 27 and 28 is per se not part of this invention but is the subject of the copending application of James F. Horst, Serial No. 359,138, filed June 2, 1953.

. The motor 10 includes a cylindrical casing 26 having top and bottom plates 27 and 28 secured thereto by annular series of studs 29 screwed into tapped holes 30 in the ends of the case. O-rings 31 of usual construction applied to a high pressure pipe 3 provide fluid tight seals between the casing and the plates 27 and 28 respectively, and pairs of O-rings 32 provide fluidtight seals around the rotor shaft where it passes through the plates 27 and 28.

The rotor is provided with'diametrically opposite, pref-.

erably integral vanes 34 dividing the annular chamber of the motor into, two chambers. Each vane is provided along itstop, side and bottom edges with sealing means preferably comprising a continuous groove 35 of rectangular cross section, in which is located a substantially U-shaped seal 36 having a rounded or circular cross section, except at the corners and forming a pressure seal between the vanes and the walls of the chamber substantially to prevent the escape of pressure fluid from one chamber to another. The ends 37 of the seals 36 may be turned at right angles to the upper and lower legs thereof and anchored in holes in therotor communicating with the grooves 35,as shown in Fig. 4.

A pair of diametrically opposite abutments or shoes 38 and 38' is mounted in the casing preferably by means of screw studs 39, and each shoe, is provided along its top, bottom and inner and outer edges with sealing means preferably comprising a continuous. groove 40 of rectangular cross section, in which is located a rectangular sealing ring 41 having a rounded ,or circular cross 'section except at the corners. The rings 41 provide a pressure seal between the shoes and the walls of the chamber, and also between the inner edges of the shoes and .the rotor 14.v Thus the vanes 34 and shoes 38 and 38' divide the annular space between the casing and the rotor into four chambers of varying volume indicated at A, A, B and B7,. Asshown in Figs. 5 and 6, chambers A and A'are interconnected preferably through the hub of rotor 14 by angular communicating ports 42, and chambers B and. B are similarly interconnected by angular communicating ports 43.

Preferably the seals 36 and 41, as well as rings 31 and 32,. are made of synthetic rubber or plastic sealing material which is resistant to the oil or other fluid used as pressure fluid in the. motor, and the seals and rings are substantially circular in cross section and distorted by pressing them in their grooves of rectangular cross section to provide a pressure seal according to well-known practice. The U-shaped seals 36 and rectangular seals 41 are molded so as to have sharp, substantially rectangular squared-off projecting portions 45 at their outer corners, extending transversely of the seals, as shown in Fig. 7, in order to insure a perfect seal, because if these corners are rounded transversely the distortion of the seals at the outer corners is sometimes not sufficient to fill in the right angled corners between the top and side surfaces within the motorchamber, and slight leaks may develop. The molded corners 45 provide positive seals around the rightangled corners at all times. The constructionof the seals is, disclosed and claimed in the copending parent application Serial No. 333,496. Thechambers A, A, B and B? may be filled with oil and the power to rotate the vanes 34 and rotor 14 may be gas, air orliquid under pressuresupplied to oil pressure tanks for forcing oil through one of the nozzles 47 or 48 which communicates with chambers A and B respectively, for rotation in one direction and to the other nozzle for rotation in the other direction. When pressure is supplied through nozzle 47, nozzle 48 acts as an exhaust port and vice versa. Each of the nozzles is preferably provided with an O-ring packing 49 where it extends through the casing, and the inner ends of the nozzles extend into grooves 50 provided on opposite sides of the shoe 38'. At their outer ends the nozzles 47. and 48 are internally threaded for attachment with pressure lines leading to the oil pressure tanks (not shown).

When the motor is used to operate a valve 11 in a pipe line, as shown in Fig. 1, which may be carrying gas under high pressure, the linesections 12 and 13 on eachside of the valve may be tapped as indicated by lines 51 and 52 which are connected through a suitable control valve to the nozzles 47 and 48 to furnish the power for oper ating the motor 10. The control valve may be actuated manually or automatically in various ways. If it is desired to actuate the control valve automatically by a change in the line pressure, the pipe line may be con nected by a tap line 53 to suitable control valve actuating means.

At their inner ends the bores 54 of the nozzles are angled laterally to terminate in seating faces 55 parallel to the inner beveled faces 56 of the shoes which alternately parallel the vanes 34 at their limits of movement. The faces 56 of each shoe 38 and 38' are at 90 to each other and the vanes rotate through 90 from adjacent one face to the other, as indicated in Figs. 2 and 3. Preferably, stop studs 57 are screwed in the faces 56 of both shoes against which the vanes abut in their extreme positions, so that the vanes are spaced from the shoes when they strike the studs at the end of 90 of travel in either direction. The studs 57 may be secured in adjusted position by set screws 58.

The novel internal shut-off means is arranged to close oflf one or the other of the nozzles 47 and 48, whichever is acting as the exhaust port, at the end of vane movement in either direction. The shut-off means comprises twospring-pressed plunger valves 60, mounted in the vanes and adapted to seat in the nozzle openings 54 in the seating faces 55 of the nozzles 47 and 48. The valves 60 are preferably conical caps of resilient oil resistant material such as neoprene for making a fluid-tight seal around the nozzle openings. Each valve cap 60 is secured on the end of a pin 61 slidably inserted in a hole 62 extending through one of the vanes 34 at right angles thereto. Preferably, the cap is secured on the pin by a split retaining ring 60a in a manner toallow slight universal movement of the cap. A small O-ring 63 surrounds the pin within the vane to prevent leakage of fluid through the hole 62. The opposite end of the pin 61 is threaded and a retaining nut 64 is screwed thereon. Between the cap 60 and the vane is a helical spring 65 urging the cap away from the vane, and the spring tension can be controlled by adjusting the nut 64. Thus when one of the valve caps 60 engages one or the other of the nozzle openings 54 in nozzles 47 and 48, it is resiliently held on its seat by the spring 65, the springs being adjusted to allow the caps to seat before the stop screws 57abut the vanes.

In the operation of the motor 10,.with the rotor in the position of Fig. 2, the lower valve 60 is shown closing off the nozzle 48 which acted as the exhaust port in the previous operation of the motor, when pressure was introduced through nozzle 47 into chamber A and through ports 42 :to chamber A, rotating the rotor counterclockwise. Now if pressure is applied through nozzle 48 into chamber B and through ports 43 to chamber B, nozzle 47 becomes the exhaust port and the rotor is rotated clockwise to the position of. Fig. 3 where the vanes abut diametrically opposite stops 57 and the upper valve closes off the exhaust port 54 in nozzle 47. Thus, the instant the rotor reaches either of its extreme positions, the exhaust port is sealed off and there can be no leakage of pressure fluid from the motor. By having the cap 60 conical and capable of slight universal movement, registry of the cap with the exhaust port, followed by a complete seal, is assured.

Before pressure is introduced into the nozzle on the pressure side of the vane, the nozzle is sealed tight by one of the shut-offs as a resultof the previous operation. The instant pressure strikes the shut-off, the spring 65 behind the shut-off yields sufficiently to admit pressure fluid into the chamber where it acts on the vanes with the elfective force of pressure times area and starts the vane to rotate. Without'the yielding movement of the shut-offs, excessively high pressure would be required to unseat the shut-01f before rotating the vane.

sesame 3-5 If it were not for the shut-oflfs 60, leakage would occur due to the tendency of the pressure fluid to seep or flow by the sealing strips 36 from the pressure side to the exhaust side of the vanes. While the seals 36 provide a' substantially fluid tight seal between'the vanes and the cylinder wall as the vanes rotate, there is bound to be some seepage past the seals when the vanes are stopped with high pressure on one side and exhaust on the other side. Accordingly, even though the pressure for operating the motor continues to be applied for a substantial period after the motor is operated, the shut offs 60 prevent leakage of fluid from the motor. For example, if the motor is used to close the pipe line valve 11, the instant the valve is closed the exhaust from motor cylinder 26 is auto matically shut ofi, preventing leakage of the fluid therefrom no matter how long the power for operating the motor is applied thereto. 1 This automatic shut off represents'a substantial saving where the pressure fluid is expensive and is exhausted to the atmosphere or to waste. Where the power is transmitted to fluid such as oil in the motor, contained in a closed circuit, it tends to prevent unbalance of the fluid in the pressure and exhaust chambers, such as would be caused by leakage from the exhaust chamber.

- In the modified form shown in Figs. 8 and 9, the two shut-off valves are located on opposite sides of one vane 34, and arranged selectively to close the nozzles 47 and 48 at opposite ends of the vane movement. In this embodiment the nozzles are located on opposite sides of the vane, for example, nozzle 47 being in chamber A adjacent to one shoe 38', and nozzle 48 being in chamber B adjacent to the other shoe 38. Stop screws 57 are secured in the shoes.

The opposed conical resilient valve heads 60A and 60B on opposite sides of the vane 34 are mounted for slight universal movement on opposite ends of the pin 61A which extends through the vane, and are backed up by compression springs 65A and 65B interposed between the valves and the vane. Preferably, the pin is slidable in two bushings 70 threaded into a bore 71 in the vane. O-ring seals 72 are provided in the bushings around the pin, and O-ring seals 73 may also be provided in the vanes around the bushings.

Between the bushings 70, the bore 71 provides a fluid chamber around a medial portion of the pin, and a piston 75 on the pin 61A fits slidably in the chamber and has sealing ring 76 thereon. A passageway 77 in the vane from the side of the vane facing chamber B, which in this case is the exhaust chamber, communicates with the remote end of chamber 74 on the opposite side of piston 75, and a passageway 78 from the side of the vane facing chamber A communicates with the remote end of chamber 74 on the other side of piston 75.

In the operation of this embodiment, when oil under pressure is introduced through nozzle 47 into chamber A to move the rotor counterclockwise, oil is exhausted from chamber B through nozzle 48. As the vane is rotated by the pressure in chamber A, oil passes through passageway 78 into chamebr 71 on the opposite side of piston 75 to force it to the right as viewed in Fig. 8. Oil also passes from the chamber B through passageway 77 to the opposite side of piston 75 but the pressure on that side is less than in chamber A.

When the piston is forced to the right as shown in Fig. 8, the spring 65B is partially compressed, and as the valve B enters the bore 54 of nozzle 48, the exhaust nozzle is completely sealed off. After the pressure entering through nozzle 47 is shut off, the seepage past the seal 36 of the vane gradually equalizes the pressure in chambers A and B which results in a very slight reverse movement of the vane. This slight reverse movement of the vane provides a corresponding amount of clearance between the right side of piston 75 and adjacent bushing 70, as indicated in Fig. 9, while the springB maintains the valve 60B tightly'closed to prevenfanyleaka'ge. "The spring may be set to resist a pressure of 5 to 10 pounds entering nozzle 48, so as to act as a check valve against pressure surges or the like below that amount of pressure. When the flow of pressure fluid is reversed, to rotate the vane in the opposite direction, pressure fluid entering through nozzle 48 can move the valve 60B against the pressure of spring 65B to the extent of the clearance on the opposite side of piston 75 before the vane is moved. The movement of the valve is suflicient to start opening the port 55 to introduce pressure fluid into'thechamber B and subject the whole area of the vane to turning pressure. 7 The embodiment of Figs. 8 and 9 insures that there will be no leakage at the exhaust port due to theslight reverse movement of the vane 'when the pressure equalizes on both sides thereof, even though the pressure is auto: matically shut off the instant the exhaust port is closed by the shut-off valve. If no spring were provided behind the shut-off valve, the slight reverse movement of the vane would tend to take the shut-off with it and open the valve. A similar condition might occur under certain conditions with the embodiment of Figs. 2 and 3, because if the pressure shut off instanteously with the closing of the exhaust port, the spring 65 behind the shut-01f 60 would not be compressed, and the slight reverse movement of the vane would open the valve.

Accordingly, the embodiment of Figs. 8 and 9 prevents leakage from the exhaust side of the motor at the end of the vane movement, under all conditions.

Obviously, one of the shut-off valves of Figs. 8 and 9 could be located in each vane if the nozzles 47 and 48 were located on opposite sides of one of the shoes 38 or 38 as in Figs. 1-7. In such case the pin 61A would project from one side of the vane for closing the exhaust nozzle, with piston 75 on the inner end of the pin Within the bore 71, instead of the pin extending through the vane to the opposite side.

What is claimed is:

1. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing pressure fluid chambers of varying volume on opposite sides of said vanes, and conduits for supplying pressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising shut-off valves mounted on opposite sides of one of the vanes for alternately closing the conduits as the rotor is rotated in opposite directions, said valves comprising a pin extending slidably through said vane, valve heads on opposite ends of said pin, and springs between the valve heads and the vane.

2. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing pressure fluid chambers of varying volume on opposite sides of said vanes, and conduits for supplying pressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising shut-off valves mounted on opposite sides of one of the vanes for alternately closing the conduits as the rotor is rotated in opposite directions, stop means on the shoes limiting movement of the vanes in either direction, said valves comprising a pin extending slidably through said vane, valve heads on opposite ends of said pin, and between the Valve heads and the vane.

3. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing pressure fluid chambers of varying volume on opposite sides of said vanes, and conduits for supplying pressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising shut-ofi valves mounted on opposite sides of one of the vanes for alternately closing the conduits as' the rotor is:

rotated in opposite directions, said valves comprising a pin extending slidably through saidvan, conical resilientv springsvalve heads mounted onopposite ends of the pin for slightuniversal movement thereon, and springs between the valve heads and the vane.

4. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary ,shoes providing pressure fluid chambers of varying volume on opposite sides of said vanes, and conduits for supplying pressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising shut-otf valves mounted on opposite sides of one of the vanes for alternately closing the conduits as the rotor is rotated in opposite directions, said valves comprising a pin extending slidably through said vane, an enlarged bore in the vane around a medial portion of the pin, a piston secured on the pin and reciprocable in said enlarged bore, and said vane having passageways leading from both sides of the vane to the remote ends of said bore whereby fluid from the varying volume chambers can enter said bore, valve heads on opposite ends of said pin, and compression springs between the valve heads and the sides of the vane.

5. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing pressure fluid chambers of varying volume on opposite sides of said vanes, and conduits,

for supplying pressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising shut-off valves mounted on opposite sides of one of the vanes for alternately closing the conduits as the rotor is rotated in opposite directions, said valves comprising a pin extending slidably through said vane, an enlarged bore in the vane around a medial portion of the pin, a piston secured on the pin and reciprocable in said enlarged bore, and saidvane having passageways leading from both sides of the vane to the remote ends of said bore whereby fluid from the varying volume chambers can enter said bore, valve heads on opposite ends of said pin, and compression springs betweenthe valve heads and the sides of the vane, each spring beingpartially compressed when the piston abutsthe end of the enlarged bore remote from said spring.

6. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing pressure fluid chambers of varying volume on opposite sides of saidvanes, and conduits for supplying pressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising shut-01f valves mounted on opposite sides of one of the vanes for alternately closing the conduits as the rotor is rotated in opposite directions, said valves comprising i a pin extending ,slidably through said vane, an enlarged bore in the vane around a medial portion of the pin, a piston secured on the pin and reciprocable in said enlarged bore, and said vane having passageways leading from both sides of the vane to the remote ends of said bore whereby fluid from the varying volume chambers can enter said bore, valve heads on opposite ends of said pin, and compression springs between the valve heads and the sides of the van e,,the springs being adapted selectively to hold the valve heads in closed position against predetermined low pressures within said conduits, and to open under operating pressures for reversing rotation of said rotor.

7. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing fluid chambers of varying volume on opposite sides of said vanes, and conduitsfor supplying pressure fluid to and exhausting it from opposite sides of i the vanes; the improvement comprising a shut-off valve mounted on one of the vanes for closing one of said conduits as the rotor is rotated in one direction, said valve comprising a pin slidable in said vane and projecting therefrom toward said conduit, an enlarged bore in the vane around the pin, a piston secured on the pin and reciprocable inisaidenlarged bore, said vane having passageways leading from both sides of said vane to the remote ends of said bore whereby fluid from the varying volume chambers can enter the bore, a valve head on the projecting end of said pin, and a compression spring between said valve head and the side of the vane.

8. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing fluid chambers of varying volume on opposite sides of said vanes, and conduits for supplying pressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising a shut-off valve mounted on one of the vanes for closing the exhaust conduit when the rotor is rotated in the direction to move said vane toward said exhaust conduit, said valve comprising a pin slidable in said vane and projecting therefrom toward said exhaust conduit, an enlarged bore in the vane around the pin, a pistonsecured on the pin and reciprocable in said enlarged bore, said vane having passageways leading from both sides of said vane to the remote ends of said bore whereby fluid from the varying volume chambers can enter the bore, a valve head on the, projecting end of said pin, and a compression spring between said valve head and the side of the vane.

9. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing fluid chambers of varying volume on opposite sides of said vanes, and conduits for supplyingpressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising a shutoff valve mounted on one of the vanes for closing one of said conduits as the rotor is rotated in one direction, said valve comprising a pin slidable in said vane and projecting therefrom toward said conduit, an enlarged bore in the vane around the pin, a piston secured on the pin and reciprocable in said enlarged bore, said vane having passageways leading from both sides of said vane to the remote ends of said bore whereby fluid from the varying volume chambers can enter the bore, a valve head on the projecting end of said pin, and a compression spring between said valve head and the side of the vane, said spring being partially compressed when the piston abuts the end of said bore remote from said spring.

10. In a hydraulic motor having a rotor provided with diametrically opposite vanes for oscillating between stationary shoes providing fluid chambers of varying volume on opposite sides of said vanes, and conduits for supplying pressure fluid to and exhausting it from opposite sides of the vanes; the improvement comprising a shut-ofl valve mounted on one of the vanes for closing one of said conduits as the rotor is rotated in one direction, said valve comprising a pin slidable in said vane and projecting therefrom toward said conduit, an enlarged bore in the vane around the pin, a piston secured on the pin and reciprocable in said enlarged bore, said vane having passageways leading from both sides of said vane to the remote ends of said bore whereby fluid from the varying volume chambers can enter the bore, a valve head on the projecting end of said pin, and a compression spring between said valve head and the side of the vane, said spring being adapted to hold said valve head in closed position against predetermined low pressures within said one conduit, and to allow opening the valve under operating pressures for reversing rotation of said rotor.

References Cited in the file of this patent UNITED STATES PATENTS 994,231 Yost June 6, 1911 2,708,907 Shafer May 24, 1955 2,778,338 Shafer Jan. 22, 1957 FOREIGN PATENTS 152,565 Great Britain Oct. 21, 1920 

